Bonafè Filippo, Dong Chaoqun, Malliaras George G, Cramer Tobias, Fraboni Beatrice
Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy.
Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge CB3 0FA, U.K.
ACS Appl Mater Interfaces. 2024 Jul 17;16(28):36727-36734. doi: 10.1021/acsami.4c08459. Epub 2024 Jul 7.
Understanding the dynamics of ion migration and volume change is crucial to studying the functionality and long-term stability of soft polymeric materials operating at liquid interfaces, but the subsurface characterization of swelling processes in these systems remains elusive. In this work, we address the issue using modulated electrochemical atomic force microscopy as a depth-sensitive technique to study electroswelling effects in the high-performance actuator material polypyrrole doped with dodecylbenzenesulfonate (Ppy:DBS). We perform multidimensional measurements combining local electroswelling and electrochemical impedance spectroscopies on microstructured Ppy:DBS actuators. We interpret charge accumulation in the polymeric matrix with a quantitative model, giving access to both the spatiotemporal dynamics of ion migration and the distribution of electroswelling in the electroactive polymer layer. The findings demonstrate a nonuniform distribution of the effective ionic volume in the Ppy:DBS layer depending on the film morphology and redox state. Our findings indicate that the highly efficient actuation performance of Ppy:DBS is caused by rearrangements of the polymer microstructure induced by charge accumulation in the soft polymeric matrix, increasing the effective ionic volume in the bulk of the electroactive film for up to two times the value measured in free water.
了解离子迁移和体积变化的动力学对于研究在液体界面运行的软质聚合物材料的功能和长期稳定性至关重要，但这些系统中溶胀过程的亚表面表征仍然难以捉摸。在这项工作中，我们使用调制电化学原子力显微镜作为一种深度敏感技术来解决这个问题，以研究掺杂十二烷基苯磺酸盐（Ppy:DBS）的高性能致动器材料聚吡咯中的电溶胀效应。我们对微结构化的Ppy:DBS致动器进行了结合局部电溶胀和电化学阻抗谱的多维测量。我们用一个定量模型解释了聚合物基质中的电荷积累，从而能够了解离子迁移的时空动力学以及电活性聚合物层中电溶胀的分布。研究结果表明，Ppy:DBS层中有效离子体积的分布不均匀，这取决于薄膜形态和氧化还原状态。我们的研究结果表明，Ppy:DBS的高效致动性能是由软质聚合物基质中电荷积累引起的聚合物微观结构重排导致的，使电活性薄膜主体中的有效离子体积增加到自由水中测量值的两倍。
